Patent GB-1317760-A (GB)
Title: Apparatus for controlling a volumetric artificial respirator
IPC: A61M16/00
Filed: 1970-07-31
Abstract: 1317760 Artificial respirators G BELFORTE 31 July 1970 [2 Aug 1969] 37126/70 Heading A5T Apparatus for controlling in the automatic mode an artificial respirator, of the type having an inflatable reservoir for containing patient supply gas and a rigid pressurisable chamber enclosing the reservoir, comprises an adjustable-frequency oscillator 9, Fig. 3, connected to binary counters 12 to 15 the outputs of which are connected to decoders 16 to 21 and to a cycle-initiating device 22, a first bistable device 5 controlled by the decoders and by the device 22, and asecond bistable device 6 controlled by the device 22 and by a trigger 7 which operates at the end of the inspiration period, the devices 5 and 6 operating an expiration control valve in the expiration circuit of the patient; the apparatus preferably also being operable in the assist mode when the devices 5 and 6 are controlled by the trigger 7 and by a sensor (67 to 71), (Fig. 10, not shown) sensing the start of spontaneous inspiration by the patient. The apparatus may utilize electronic or preferably fluidic logic elements. A cycle is initiated when bistables 5, 6 switch to give outputs C and F respectively. Signal C closes said expiration control valve (VB hereafter) to allow inspiration, and signal F closes a quick-discharge valve on said rigid chamber and simultaneously a valve 44, Fig. 6, opens to allow air into the chamber to deflate the reservoir. When the reservoir is closed, a sensor (63 to 66), (Fig. 9, not shown) sends a signal Q to trigger 7 producing an output G resetting bistables 5 in the automatic mode, and also bistable 5 in the assist mode, so that valves VB, 44 operate to start the expiration period. Blocks 23-26 determine and indicate whether signal G occurs before or after one eighth of a cycle in the automatic mode. In the automatic mode, bistable 5 is reset by a signal A from the decoders. Air is supplied to the apparatus via a valve 33, Fig. 6, filter 34, a regulator 35 supplying the fluidic logic and a switching block 37 controlling change-over from automatic to assist modes, the valve 44 being supplied via reducer 36 and valve 43. Block 37 is push-button controlled to give output signals V and S corresponding to operative and inoperative respirator, and H and K corresponding to automatic or assist mode respectively. The signals from block 37 control a block 38 charging over connections to, for example, bistables 5, 6. The block 39 resets the counters and a block 40 controls a valve 42 supplying devices only operating in the automatic mode, and signal S controls valve 43 and a valve 41 supplying devices operating in either mode. A multiway switch 45 is used to selectively supply the decoding devices 16 to 21 to vary the point at which signal A is sent to bistable 5, i.e. to vary the inspiration/ expiration ratio. The Sensor (67 to 71), Fig. 10, for sensing the start of spontaneous breathing comprises a fluidic amplifier (67) and a hollow elastic valve (68) connected to the patient so that it opens and closes a control port of the amplifier as the patient inspires and expires. The means for signalling termination of air delivery to the patient comprises a nozzle (63), Fig. 9, freely discharging air to the rigid chamber and fed via a resistor (64), the pressure Q between nozzle (63) and resistor (64) being fed to the trigger 7 having a second input receiving a reference pressure. When the inflatable reservoir has discharged, an abutment closes the nozzle (63) and pressure Q increases and when it reaches the reference pressure the signal G, Fig. 3, is produced.